Method and apparatus for use in balancing ligaments of a knee

ABSTRACT

An apparatus for use in performing an orthopaedic surgical procedure on a patient includes at least one femoral paddle and a tibial paddle. At least one of the femoral paddle and the tibial paddle is movable away from the other. The apparatus also includes a sensor configured to generate a signal indicative of a force applied to the femoral paddle or the tibial paddle. The apparatus may be communicatively coupled to a computer assisted orthopaedic surgery system.

TECHNICAL FIELD

The present disclosure relates generally to methods and apparatus foruse in the performance of orthopaedic procedures such as kneereplacement procedures.

BACKGROUND

In some orthopaedic surgical procedures, such as a total kneereplacement procedure, ligament balancing devices (commonly known asligament balancers) may be used to balance the surrounding soft tissue(i.e., ligaments) of a patient's joint. For example, in a total kneereplacement procedure, ligament balancing may be performed to ensure agenerally rectangular shaped extension gap and a generally rectangularshaped flexion gap at a predetermined joint force value between thepatient's natural or prosthetic proximal tibia and the patient's naturalor prosthetic distal femur. To do so, a ligament balancer may be used tomeasure the medial and lateral joint forces and the medial and lateralgap distances when the patient's leg is in extension (i.e., thepatient's tibia is positioned at about 0 degrees relative to thepatient's femur) and in flexion (i.e., the patient's tibia is positionedat about 90 degrees relative to the patient's femur). In eitherextension or flexion, if the medial and lateral gap distances are notapproximately equal (i.e., do not form a generally rectangular shapedjoint gap) at the predetermined joint force value, ligament release maybe performed to equalize the medial and/or lateral gap distances. Atypical ligament balancer includes manually operated mechanicalmechanisms, such as springs, to determine the joint force and to adjustthe extension/flexion gap distance.

SUMMARY

According to one aspect, an apparatus for use in performing anorthopaedic surgical procedure on a patient is disclosed. The apparatusmay include one or more femoral paddles configured to contact a naturalor prosthetic distal femur of a patient. The apparatus may also includeone or more tibial paddles configured to contact a natural or prostheticproximal tibia of the patient. At least one of the femoral paddle and/orthe tibial paddle is movable away from the other. The apparatus mayinclude a force sensor operatively coupled to the femoral paddle and/orthe tibial paddle. The force sensor generates an output signal that isindicative of the magnitude of the force applied to the respectivepaddle. The apparatus may also include a distance sensor. The distancesensor generates an output signal that is indicative of the distancebetween the femoral and tibial paddles.

The apparatus may further include one or more controllers that determinea joint force value based on the output signal of the force sensor and adistance value based on the output signal of the distance sensor. Theapparatus may also include a user interface and may display the forcevalue and/or distance value to a user of the apparatus on the userinterface via a display. The display may be a digital display, a seriesof LEDs, or the like. The apparatus may include actuators coupled to thepaddles. The user may control the movement of the paddles by selectingan appropriate button from the user interface. In response, thecontroller controls the actuator to move the paddles. The apparatus mayalso transmit the force values and/or distance values to a computerassisted orthopaedic surgery system. In addition, the computer assistedorthopaedic surgery system may control functions of the apparatus bytransmitting control and/or data signals to the controllers of theapparatus.

According to another aspect, a method for using a ligament balancer isdisclosed. The method may include inserting the ligament balancerbetween a distal femur and a proximal tibia of the patient. The methodmay also include moving at least one of a femoral paddle and a tibiapaddle away from the other paddle and generating an output signal thatis indicative of a force applied to one of the paddles. The method mayalso include generating an output signal indicative of a distancebetween the paddles. The output signals and/or values derived therefrommay be transmitted to a computer assisted orthopaedic surgery system.

The above and other features of the present disclosure, which alone orin any combination may comprise patentable subject matter, will becomeapparent from the following description and the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description particularly refers to the following figures,in which:

FIG. 1 is a perspective view of an electronic ligament balancer;

FIG. 2 is another perspective view of the ligament balancer of FIG. 1,note that the femoral paddles are positioned in different positions inFIG. 2;

FIG. 3 is a simplified block diagram of an electrical system of theligament balancer of FIG. 1; and

FIG. 4 is a simplified block diagram of a computer assisted orthopaedicsurgery system communicatively coupled to the ligament balancer of FIG.1.

DETAILED DESCRIPTION OF THE DRAWINGS

While the concepts of the present disclosure are susceptible to variousmodifications and alternative forms, specific exemplary embodimentsthereof have been shown by way of example in the drawings and willherein be described in detail. It should be understood, however, thatthere is no intent to limit the concepts of the present disclosure tothe particular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

Referring to FIG. 1, a ligament balancer 10 for use in an orthopaedicsurgical procedure includes a tibial paddle 12, a first femoral paddle14, and a second femoral paddle 16. The femoral paddle 14 is positionedvertically over and movable away from the tibial paddle 12. Similarly,the femoral paddle 16 is positioned vertically over and movable awayfrom the tibial paddle 12. The tibial paddle 12 is configured to contacta proximal tibia of the patient. As used herein, the term “proximaltibia” is intended to refer to the natural or prosthetic proximal end ofa patient's tibia. The tibial paddle 12 may include a mounting slot oraperture 13 configured to receive additional instrumentation such as aflexion adapter, a Ranawat block, and/or an anterior/posterior resectionguide. The femoral paddles 14, 16 are configured to contact a distalfemur of the patient. As used herein, the term “distal femur” isintended to refer to the natural or prosthetic distal end of thepatient's femur. In use, one of the femoral paddles 14, 16 contacts themedial side of the patient's femur and the other femoral paddle 14, 16contacts the lateral side of the patient's femur depending on whichfemur-tibia joint of the patient is being operated on. For the followingdescription, it will be assumed that the ligament balancer 10 is beingused on a patient's left knee. Accordingly, femoral paddle 14 andcomponents associated therewith may be described hereinafter as medialfemoral paddle 14 and components. Similarly, the femoral paddle 16 andcomponents associated therewith may be described hereinafter as lateralfemoral paddle 16 and components.

Each of the femoral paddles 14, 16 is coupled to respective cylinders18, 20. The cylinders 18, 20 are extendable out of and retractable intorespective housings 22, 24. In the illustrative example, the housings22, 24 are secured to each other via the tibial paddle 12. The medialfemoral paddle 14 may be moved away from or toward the tibia paddle 12by extending or retracting the cylinder 18. The lateral femoral paddle16 may be moved away from or toward the tibia paddle 12 by extending orretracting the cylinder 20. It should be appreciated that each femoralpaddle 14, 16 is independently movable. For example, as illustrated inFIG. 2, the medial femoral paddle 14 may be moved away from the tibialpaddle 12 to a distance 70 that is greater than a distance 72 that thelateral femoral paddle 16 is moved away from the tibial paddle 12.Although the femoral paddles 14, 16 are described herein as movablerelative to the tibial paddle 12, it should be appreciated that in otherembodiments the tibial paddle 12 may be movable rather than or inaddition to the femoral paddles 14, 16.

Movement of the femoral paddles 14, 16 may be performed via manual orautomated means. For example, in some embodiments, the ligament balancer10 includes knobs 26, 28 operatively coupled, such as by a screwmechanism, to the cylinders 18, 20, respectively. By manually turningone or both knobs 26, 28 in a clockwise or counterclockwise direction,the cylinders 18, 20 may be extended from or retracted into therespective housings 18, 20 so as to move the femoral paddles 14, 16. Inother embodiments, additional or alternative devices for manually movingthe femoral paddles 14, 16 away from the tibial paddle 12 may beincluded. As will be described below in greater detail, in yet otherembodiments, such manual adjustment of the ligament balancer may bereplaced or included with automated mechanisms.

The ligament balancer 10 includes a force sensor 30, a distance sensor32, and an actuator 34 positioned in the housing 22. The ligamentbalancer 10 also includes a force sensor 50, a distance sensor 52, andan actuator 54 positioned in the housing 24. The force sensor 30 isoperatively coupled to the cylinder 18 and generates an output signal,such as a voltage signal, indicative of a magnitude of force applied tothe medial femoral paddle 14. The force sensor 50 is operatively coupledto the cylinder 20 and generates an output signal, such as a voltagesignal, indicative of a magnitude of force applied to the lateralfemoral paddle 16. In one particular embodiment, the force sensors 30,50 are embodied as a load cells, such as miniature load cells.

The distance sensor 32 generates an output signal indicative of a medialdistance 70 (see FIG. 2) between the medial femoral paddle 14 and thetibial paddle 12. The distance sensor 52 generates an output signalindicative of a lateral distance 72 (see FIG. 2) between the lateralfemoral paddle 16 and the tibial paddle 12. In some embodiments, thedistance sensors 32, 52 are electrical devices and generate electricaloutput signals indicative of the distances 70, 72, respectively. Inother embodiments, the distance sensors 32, 52 may be replaced withmechanical distance indicators that create visual signals indicative ofthe distances 70, 72. For example, the distance sensors 32, 52 may bereplaced with indicator needles or other visual indicators coupled tothe cylinders 18, 20, and each housing 22, 24 may include a distancescale associated with each needle from which the medial and lateraljoint gap distances may be obtained based on the position of therespective needle.

The actuator 34 is operatively coupled to the cylinder 18 and isoperable to extend or retract the cylinder 18 in response to acorresponding control signal. Similarly, the actuator 54 is operativelycoupled to the cylinder 20 and is operable to extend or retract thecylinder 20 in response to a corresponding control signal. In oneparticular embodiment, the actuators 34, 54, are embodied as steppermotors. In another embodiment, the actuators 34, 54 are embodied aslinear actuators. However, the actuators 34, 54 may be embodied as anyprime mover devices operable to extend or retract the cylinders 18, 20.Although the illustrative ligament balancer 10 includes the forcesensors 30, 50, the distance sensors 32, 52, and the actuators, 34, 54,in some embodiments, the ligament balancer 10 may include only the forcesensors 30, 50, only the distance sensors 32, 52, only the actuators,34, 54, or any combination thereof.

The ligament balancer 10 illustrated in FIGS. 1 and 2 also includes auser interface 36, a controller 38, and a power supply 40 positioned onor in the housing 22. The ligament balancer 10 also includes a userinterface 56, a controller 58, and a power supply 60 positioned on or inthe housing 24. The user interface 36 may include a display screen 42and a number of user buttons 44. Similarly, the user interface 56 mayinclude a display screen 62 and a number of user buttons 64. In otherembodiments, however, the display screens 42, 62 may be replaced with aseries of light-emitting-diodes (LEDs) or a collection of visualindicators to provide simplified visual feedback to the user of theligament balancer 10. Additionally, in some embodiments, the userinterfaces 36, 56 may be replaced by a remote user interface(s) such asa user interface module that is separate from the housings 22, 24. Insuch an embodiment, the remote user interface(s) may communicate withthe controllers 38, 58 via wired or wireless communication.

The controllers 38, 58 may be embodied as any type of controllersincluding, for example, general purpose micro-controllers,microprocessors, or application specific integrated circuits (ASICs).The power supplies 40, 60 may be embodied as any devices capable ofsupplying power to the other respective components such as controllers38, 58, respectively. In one particular embodiment, the power supplies40, 60 are embodied as replaceable batteries. In another embodiment, thepower supplies 40, 60 are embodied as rechargeable battery packs. Insuch embodiments, the ligament balancer 10 may include appropriatecharging contacts to allow the recharging of the battery packs. Althoughin the embodiment illustrated in FIG. 1, the ligament balancer 10includes two user interfaces, two controllers, and two power supplies,it should be appreciated that in other embodiments the ligament balancer10 may include only one user interface, one controller, and/or one powersupply. For example, the ligament balancer 10 may include a singlecontroller positioned in one of the housings 22, 24 and communicativelycoupled to each of the force sensors 30, 50, the distance sensors 32,52, and the actuators 34, 54. Similarly, the ligament balancer 10 mayinclude a single user interface that is communicatively coupled to eachof the controllers 38, 58 (or to a single controller).

Referring now to FIG. 3, the interconnection of the components includedin the medial housing 22 will be described below with the understandingthat such description is also applicable to the components included inthe lateral housing 24. In addition, it should be further understoodthat in some embodiments of the ligament balancer 10 only onecontroller, one user interface, and/or one power supply may be included.Again, the following description is applicable to such embodiments aswell.

The controller 38 is communicatively coupled to the force sensor 30, thedistance sensor 32, and the actuator 34 via a number of interconnects80, 82, and 84, respectively. The interconnects 80, 82, 84 may be anytype of interconnect capable of enabling communication between thesensor 30, the sensor 32, the actuator 34 and the controller 38 such aswires, printed-circuit-board (PCB) traces, wireless connections, and thelike. In addition, the controller 38 is communicatively coupled to theuser interface 36 via interconnects 86 and to the power supply 40 viainterconnects 88. The controller 38 may further include a receiver,transmitter, or transceiver 90 and a memory device 92 such as a randomaccess memory (RAM) device.

The controller 38 is configured with the appropriate hardware, software,and/or firmware to be responsive to the user commands received via theuser interface 36. As such, a surgeon may interact with the ligamentbalancer 10 via the user interface 36 to control functions of theligament balancer 10. For example, by use of one of the buttons 44 ofthe user interface 36, the surgeon can control the actuator 34 to movethe medial femoral paddle 14 relative to the tibial paddle 12. Inaddition or alternatively to the user interface 36, in some embodiments,the surgeon may control the functions of the ligament balancer 10 (e.g.,moving the femoral paddle 14) via voice commands. In such embodiments,the ligament balancer 10 may include a microphone or other device forreceiving voice commands from the surgeon. To facilitate such a feature,the controller 38 may include voice recognition software or devices tofacilitate voice control of the ligament balancer 10.

In addition, the controller 38 receives measurement data from the forcesensor 30 and the distance sensor 32 via the interconnects 80, 82,respectively. The controller 38 may display the measurement data to theuser via the user interface 36 and/or store the measurement data in thememory device 92 for later use. For example, while a patient's leg ispositioned in extension, a surgeon may move the medial femoral paddle 14away from the tibia paddle 12 until a predetermined medial joint forcevalue is achieved as indicated by the force sensor 32 and displayed tothe surgeon via the user interface 36. The surgeon may then select oneof the buttons 44 to cause the controller 38 to store the medial jointforce value and/or the medial joint gap distance, as indicated by theoutput signal of the distance sensor 32, in the memory device 92. Thesurgeon may then position the patient's leg in flexion, reinsert theligament balancer 10, and select another one of the buttons 44 to causethe actuator 34 to move the medial femoral paddle 14 to a positionhaving the same medial joint force as the stored medial joint forcevalue. In this respect, actuation of the femoral paddles 14, 16 may beautomated or semi-automated without direct control of the actuators 34,54 by the user.

Referring now to FIG. 4, the controller 38 of the ligament balancerapparatus 10 may be configured to communicate with an externalcontroller, computer, or system such as a computer assisted orthopaedicsurgery (CAOS) system 94 by use of the transceiver 90 (either wired orwirelessly). In one particular embodiment, the CAOS system 94 isembodied as a Ci™ system commercially available from Depuy Orthopaedics,Inc. of Warsaw, Ind. The controller 38 may communicate with the CAOSsystem 94 via a communication link 96. The communication link 96 may beany type of communication link including a wired or wirelesscommunication link and may use any type of suitable communicationtechnology and/or protocol including, but not limited to, Ethernet, USB,TCP/IP, Bluetooth, ZigBee, Wi-Fi, Wireless USB, and the like. Onecommunication network that may be used as the communication link 96 toenable wireless communication between the controller 38 and the CAOSsystem 94 is described in currently pending and commonly owned U.S.patent application Ser. No. 11/024,905 entitled “Medical DeviceCommunications Network”, which was filed on Dec. 29, 2004, the entiretyof which is expressly incorporated herein by reference.

In some embodiments, the controller 38 transmits measurement datareceived from the force sensor 30 and/or the distance sensor 32 to theCAOS system 94. The CAOS system 94 may then display the measurement datato the surgeon via a display device (not shown) such as a monitor or thelike included in the CAOS system 94 to give the surgeon visual feedbackas the surgeon is operating the ligament balancer 10. The CAOS system 94may also use the measurement data in various calculations or algorithmsto determine, for example, surgical suggestions, anatomical simulationsresulting from a proposed surgical procedure or step, and the like.

In addition, the CAOS system 74 may communicate with the ligamentbalancer 10 to control functions of the ligament balancer 10. Forexample, while a patient's leg is in positioned in extension, a surgeonmay move the medial femoral paddle 14 and the lateral femoral paddle 16away from the tibia paddle 12 until a predetermined medial and lateraljoint force value is achieved as indicated by the force sensors 32, 52,respectively. The surgeon may then select one of the buttons 44 and/orone of the buttons 64 to transmit the medial/lateral joint force valuesand/or the medial/lateral joint gap distances to the CAOS system 94. TheCAOS system 94 stores the values for later use. The surgeon may thenposition the patient's leg in flexion, reinsert the ligament balancer10, and interact with the CAOS system 94 (e.g., by selecting a button onthe CAOS system 94, providing a verbal command to the CAOS system 94, orthe like) to cause the CAOS system 94 to transmit control signalsincluding the stored medial/lateral joint force values and/or the storedmedial/lateral joint gap distances to the ligament balancer 10. Inresponse, the controller 38 controls the actuator 34 to move the medialfemoral paddle 14 to a position having the same medial joint force asthe medial joint force value received from the CAOS system 94.Similarly, the controller 58 controls the actuator 54 to move thelateral femoral paddle 16 to a position having the same lateral jointforce as the lateral joint force value received from the CAOS system 94.Accordingly, the system 94 may control the functions of the ligamentbalancer 10 while providing the surgeon with visual feedback data duringthe surgical procedure.

The ligament balancer 10 may be used to assist a surgeon in balancingligaments of a knee of a patient. To do so, the patient's knee ispositioned in extension (i.e., the patient's tibia is positioned atabout 0 degrees relative to the patient's femur). The ligament balancer10 is then inserted between the patient's distal femur and proximaltibia. Depending upon the surgical procedure being performed and/or thesurgeon's general surgical practice, the ligament balancer 10 may beinserted prior to any resection of the bones of the knee, afterresection, after knee replacement trials have been positioned on therespective bones, or after the permanent prosthetic knee replacementcomponents have been implanted in the patient. Regardless, the ligamentbalancer 10 is positioned between the patient's femur and tibia suchthat the femoral paddles 14, 16 contact the natural or prosthetic distalfemur and the tibial paddle 12 contacts the natural or prostheticproximal tibial.

Once the ligament balancer is properly positioned, the surgeon may movethe femoral paddles 14, 16 away from the tibial paddle 12 until apredetermined medial and lateral joint force is achieved. This may beaccomplished manually by turning the knobs 26, 28 until the desiredjoint force value is achieved. Alternatively, this may be accomplishedby selecting one of the buttons 44, 64 of the user interfaces 36, 56 tocause the actuators 34, 54 to move the femoral paddles 14, 16 until thedesired joint force value is achieved. In some embodiments, this mayalso be accomplished by supplying the CAOS system 94 with the desiredjoint force value. In response, the CAOS system 94 transmits theappropriate control signals to the ligament balancer 10 to cause theactuators 34, 54 to move the femoral paddles 14, 16 away from the tibialpaddle 12 until the desired joint force value is achieved.

Each of the femoral paddles 14, 16 may be moved separately andindependently of each other. Because of irregularities in the patient'sanatomy, the femoral paddles 14, 16 may need to be moved to differentdistances to achieve the same desired joint force value. If so, theextension gap (i.e., the gap between the distal femur and the proximaltibia when the knee is in extension) will not have a rectangular shape.Because a generally rectangular shaped extension gap is desirable, thesurgeon may perform ligament release on one or more ligaments to allowthe femoral paddles 14, 16 to be equally positioned while maintainingthe desired joint force value.

It should be understood that as the surgeon is moving the femoralpaddles 14, 16, the medial and lateral joint forces (i.e., the forcesbeing applied to each paddle 14, 16) are determined by the force sensors30, 50, respectively. The controller 38 calculates a force value basedon the output signal of the force sensor 30 and displays the force valueto the surgeon via the display 42 of the user interface 36. Similarly,the controller 58 calculates a force value based on the output signal ofthe force sensor 50 and displays the force value to the surgeon via thedisplay 62 of the user interface 56. The force values displayed on theuser interfaces 36, 56 may be numerical values or may be represented bya number of LEDs. In some embodiments, the distance 70 which the medialfemoral paddles 14 is moved away from the tibial paddle 12 is determinedby the distance sensor 32 and also displayed to the surgeon via the userinterface 36. Similarly, the distance 72 which the lateral femoralpaddles 16 is moved away from the tibial paddle 12 is determined by thedistance sensor 52 and also displayed to the surgeon via the userinterface 56. Further, in some embodiments, the force values and/ordistance values may be transmitted to the CAOS system 94. The CAOSsystem 94 may display the force and/or distance values to the surgeon toprovide a visual feedback to the surgeon as the surgeon is manipulatingthe femoral paddles 14, 16. Further, the CAOS system 94 may haveadditional sensors or devices to determine when the desirablerectangular shaped extension gap is achieved and alert the user to such(e.g., by an audible or visual alert).

In addition to displaying the force values and distance values to thesurgeon, the controllers 38, 58 may store the values for later use. Forexample, once the surgeon has moved the medial femoral paddle 14 toachieve the desired medial joint force value, the surgeon may select oneof the buttons 44 to cause the controller 38 to store the medial jointforce value and, in some embodiments, the distance 70 at which themedial femoral paddle 14 is moved away from the tibial paddle 12.Similarly, once the surgeon has moved the lateral femoral paddle 16 toachieve the desired lateral joint force value, the surgeon may selectone of the buttons 64 to cause the controller 58 to store the lateraljoint force value and, in some embodiments, the distance 72 at which thelateral femoral paddle 16 is moved away from the tibial paddle 12. Inaddition or alternatively, the CAOS system 94 may store the joint forcevalues and/or distance values for later use.

After the surgeon has achieved the desired extension gap and performedany necessary ligament release, the femoral paddles 14, 16 are movedtoward the tibial paddle 12 so that the ligament balancer 10 may beremoved from the patient's knee joint. The patient's knee is thenpositioned in flexion (i.e., the patient's tibia is positioned at about90 degrees relative to the patient's femur) and the ligament balancer 10is reinserted between the patient's distal femur and proximal tibia. Thefemoral paddles 14, 16 are again moved away from the tibia paddle 12until the desired medial and lateral joint force values are achieved. Todo so, the surgeon may select one of the buttons 44 of the userinterface 36 to move the medial femoral paddle 14 away from the tibialpaddle 12 until the desired medial joint force value, as determined bythe force sensor 30, is achieved. Similarly, the surgeon may select oneof the buttons 64 of the user interface 56 to move the lateral femoralpaddle 16 away from the tibial paddle 12 until the desired lateral jointforce value, as determined by the force sensor 50, is achieved.Typically, it is desirable to use the same force value for both theflexion joint force and the extension joint force.

In another embodiment, the surgeon may select another one of the buttons44 to cause the controller 38 to retrieve the stored medial joint forcevalue from memory. The controller 38 then controls the actuator 34 tomove the medial femoral paddle 14 away from the tibial paddle 12 untilthe medial joint force, as measured by the joint force sensor 30, equalsthe retrieved medial joint force value. Similarly, the surgeon mayselect another one of the buttons 64 to cause the controller 58 toretrieve the stored lateral joint force value from memory. Thecontroller 58 then controls the actuator 54 to move the lateral femoralpaddle 16 away from the tibial paddle 12 until the lateral joint force,as measured by the joint force sensor 50, equals the retrieved lateraljoint force value.

In yet another embodiment, the CAOS system 94 controls the movement ofthe femoral paddles 14, 16 by transmitting control signals to therespective controllers, 38, 58. For example, after the ligament balancer10 has been reinserted into the knee area of the patient, the surgeonmay press another button on the user interface 36 and/or on the userinterface 56 to cause the controllers 38, 58 to send a ready signal tothe CAOS system 94 informing the CAOS system 94 that the ligamentbalancer 10 is ready to receive control signals. In response to theready signal, the CAOS system 94 retrieves the stored medial and lateraljoint force values from memory and transmits the retrieved values to therespective controllers 38, 50. The controller 38 then controls theactuator 34 to move the medial femoral paddle 14 away from the tibialpaddle 12 until the medial joint force, as measured by the joint forcesensor 30, equals the received medial joint force value. The controller58 controls the actuator 54 to move the lateral femoral paddle 16 awayfrom the tibial paddle 12 until the lateral joint force, as measured bythe joint force sensor 50, equals the received lateral joint forcevalue.

In yet a further embodiment, the surgeon may control the movement of thefemoral paddles 14, 16 via the CAOS system 94 rather than the respectiveuser interfaces 36, 56. For example, the user may enter in a desiredjoint force value into the CAOS system 94. In response, the CAOS system94 communicates the entered joint force value to the ligament balancer10 to cause the movement of the femoral paddles 14, 16 until the desiredjoint force value is achieved.

Once the femoral paddles 14, 16 have been moved to the appropriatepositions to achieve the desired joint force values, the surgeon may, ifdesirable, perform any necessary ligament release, as described above,to develop a more rectangular shaped flexion gap. After the ligamentrelease is preformed, the femoral paddles 14, 16 are moved toward thetibial paddle 12 and the ligament balancer 10 is removed from the kneearea of the patient.

Although the ligament balancer 10 has been described herein in referenceto a knee joint of a patient, it should be understood that the ligamentbalancer 10 may be used on other joints of the patient. For example, theligament balancer 10 may be used on an elbow joint of the patient. Assuch, it should be appreciated that although some of the components havebeen described in reference to certain bones of the patient (e.g.,femoral and tibial paddles), such components would be configured to beused on or with the appropriate bones of the patient's joint beingoperated on.

While the disclosure has been illustrated and described in detail in thedrawings and foregoing description, such an illustration and descriptionis to be considered as exemplary and not restrictive in character, itbeing understood that only illustrative embodiments have been shown anddescribed and that all changes and modifications that come within thespirit of the disclosure are desired to be protected.

There are a plurality of advantages of the present disclosure arisingfrom the various features of the apparatuses, systems, and methodsdescribed herein. It will be noted that alternative embodiments of theapparatuses, systems, and methods of the present disclosure may notinclude all of the features described yet still benefit from at leastsome of the advantages of such features. Those of ordinary skill in theart may readily devise their own implementations of the systems andmethods that incorporate one or more of the features of the presentinvention and fall within the spirit and scope of the present disclosureas defined by the appended claims.

1. An apparatus for use in performing an orthopaedic surgical procedureon a patient, the apparatus comprising: a tibial paddle configured tocontact a proximal tibia of the patient; a femoral paddle configured tocontact a distal femur of the patient and positioned over the tibialpaddle; means for moving at least one of the femoral paddle and thetibial paddle away from the other; and a sensor configured to generatean electrical output signal indicative of a force applied to at leastone of the femoral paddle and the tibial paddle.
 2. The apparatus ofclaim 1, wherein the means for moving the at least one of the femoralpaddle and the tibial paddle includes an actuator operatively coupled tothe at least one of the femoral paddle and the tibial paddle to move theat least one of the femoral paddle and the tibial paddle in response toa control signal.
 3. The apparatus of claim 2, wherein the actuator is astepper motor.
 4. The apparatus of claim 2, wherein the actuator is alinear actuator.
 5. The apparatus of claim 1, wherein the sensor is aload cell.
 6. The apparatus of claim 1, further comprising a distancesensor configured to generate a distance signal indicative of a distancebetween the femoral and tibial paddles.
 7. The apparatus of claim 1,further comprising a controller and a user interface, the controllerconfigured to (i) receive the electrical output signal from the sensor,(ii) determine a force value based on the electrical output signal, and(iii) display the force value on the user interface.
 8. The apparatus ofclaim 7, wherein the user interface includes a number of buttons.
 9. Theapparatus of claim 7, wherein the user interface includes a display. 10.The apparatus of claim 7, wherein the controller is responsive to userinputs received via the user interface to control the means for movingthe at least one of the femoral paddle and the tibial paddle.
 11. Theapparatus of claim 7, wherein the controller includes a memory deviceand is configured to store a digital representation of the force appliedto at least one of the femoral paddle and the tibial paddle based on theoutput signal.
 12. The apparatus of claim 7, further comprising adistance sensor configured to generate an electrical distance signalindicative of a distance between the femoral and tibial paddles, andwherein the controller is configured to (i) receive the electricaldistance signal, (ii) determine a distance value based on the electricaldistance signal, and (iii) display the distance value on the userinterface.
 13. The apparatus of claim 12, wherein the controllerincludes a memory device and is configured to store a digitalrepresentation of the distance signal.
 14. The apparatus of claim 13,wherein the controller is responsive to a user input received via theuser interface to retrieve a stored distance value from the memorydevice and control the means for moving the at least one of the femoralpaddle and the tibial paddle to move the at least one of the femoralpaddle and the tibial paddle away from the other to a distance equal tothe stored distance value.
 15. The apparatus of claim 1, furthercomprising a transmitter configured to transmit measurement data. 16.The apparatus of claim 15, wherein the measurement data includes dataindicative of the force applied to the femoral paddle.
 17. The apparatusof claim 15, wherein the measurement data includes data indicative of adistance between the femoral paddle and the tibial paddle.
 18. Theapparatus of claim 1, further comprising a receiver configured toreceive control signals from a computer assisted orthopedic surgicalsystem.
 19. The apparatus of claim 18, further comprising a controllercommunicatively coupled to the receiver and configured to control themeans for moving the at least one of the femoral paddle and the tibialpaddle in response to the control signals.
 20. A method of operating aligament balancer during the performance of an orthopaedic surgicalprocedure, the method comprising: moving at least one of a femoralpaddle and a tibial paddle away from the other; and generating anelectrical output signal indicative of a force applied to at least oneof the femoral paddle and the tibial paddle.
 21. The method of claim 20,further comprising generating an output signal indicative of thedistance between the femoral paddle and the tibial paddle.
 22. Themethod of claim 20, wherein the generating step includes transmittingdata indicative of the force applied to the at least one of the femoralpaddle and the tibial paddle to a computer assisted orthopaedic surgerysystem.
 23. The method of claim 22, wherein transmitting data includeswirelessly transmitting the data.
 24. The method of claim 20, whereinthe moving step includes controlling an actuator coupled to the at leastone of the femoral paddle and the tibial paddle.
 25. The method of claim20, further comprising the steps of: retrieving a first force value froma memory device; determining a second force value based on theelectrical output signal; and wherein the moving step includes movingthe at least one of the femoral paddle and the tibial paddle away fromthe other until the second force value equals the first force value. 26.A ligament balancer comprising: a paddle configured to contact aproximal femur of a patient; and a sensor configured to generate anelectrical output signal indicative of a force applied to the paddle.27. A ligament balancer comprising: a first paddle configured to contacta proximal tibia of a patient; a second paddle configured to contact adistal femur of the patient, at least one of the first and secondpaddles being movable away from the other; and a sensor configured togenerate an electrical output signal indicative of a distance betweenthe first and second paddles.
 28. A ligament balancer comprising: apaddle configured to contact a distal femur of a patient and movablebetween a first and second position; and an electrically driven actuatorconfigured to move the paddle between the first and second positions inresponse to a control signal.
 29. The ligament balancer of claim 28,wherein the electrically driven actuator is a stepper motor.
 30. Theligament balancer of claim 28, wherein the electrically driven actuatoris a linear actuator.